Valve timing control device for internal combustion engine

ABSTRACT

A valve timing control device for an internal combustion engine, the valve timing control device includes: a housing; a vane rotor; a lock hole; a lock member; an urging member; a connection passage provided to the vane rotor, and connected to the bolt insertion hole and the back pressure chamber; and an annular passage which is formed between an inner circumference surface of the bolt insertion hole, and an outer circumference surface of a shaft portion of the cam bolt, and which includes one end portion connected to the connection passage, and the other end portion connected to a drain hole formed in the cam shaft.

TECHNICAL FIELD

This invention relates to a valve timing control device for an internal combustion engine which is configured to variably control opening and closing timings of an intake valve and an exhaust valve of the internal combustion engine in accordance with a driving state.

BACKGROUND ART

There is a conventional valve timing control device which is described in a patent document 1 described below, and so on, and which is applied to an exhaust valve side.

This valve timing control device includes a housing to which a rotational force is transmitted from a crank shaft through a timing belt; a vane rotor which is received within the housing, which is arranged to be rotated relative to the housing, and which is fixed to an end portion of the cam shaft; a lock pin which is provided within a sliding hole formed in the vane rotor in an axial direction to be moved within the sliding hole, and which has a tip end portion arranged to be engaged with a lock hole formed in a rear plate of the housing to restrict the relative rotation of the vane rotor with respect to the housing; a coil spring elastically mounted on a rear portion side of the sliding hole, and which is arranged to urge the lock pin toward the lock hole; and a connection hole formed in the vane rotor to penetrate through the vane rotor in the axial direction, and which is arranged to introduce a hydraulic fluid within back pressure chambers to an engine.

Moreover, there is a torsion spring which is provided within a front end of the housing, which includes one end fixed to the front plate of the housing, and the other end inserted and fixed in the connection hole, and which is arranged to relatively rotate the vane rotor on an advance angle side.

Furthermore, a hydraulic fluid supplied from an oil pump through an electromagnetic switching valve to retard angle chambers is simultaneously supplied to a pressure receiving chambers formed in the lock hole at a start of the engine. The lock pin is arranged to be moved by this hydraulic fluid against a spring force of the coil spring in a retracting direction, so that the lock with respect to the lock hole is released.

PRIOR ART DOCUMENT Patent Document

Patent Document 1: Japanese Patent Application Publication No. 2011-132404

SUMMARY OF THE INVENTION Problems Which The Invention is Intended to Solve

However, in the valve timing control device described in the patent document 1, the connection hole arranged to discharge the hydraulic fluid from the back pressure chamber in formed in the vane rotor to penetrate through the vane rotor in the axial direction. Accordingly, it is necessary to increase an outside diameter of the vane rotor to ensure the forming space for the penetrating-through connection hole. Therefore, the radial size of the entire device including the vane rotor and the housing is forced to be increased.

It is, therefore, an object of the present invention to provide a valve timing control device which includes a passage that is arranged to discharge oil and air within a back pressure chamber, and that can be formed without increasing an outside diameter of a vane rotor, and which can suppress an increase of an entire size.

Means for Solving the Problem

According to one aspect of the present invention, a valve timing control device for an internal combustion engine, the valve timing control device comprises: a housing to which a rotational force is transmitted from a crank shaft, and which includes an operation hydraulic chamber formed therein; a vane rotor which includes a bolt insertion hole, which is fixed at one end portion of a cam shaft by a cam bolt inserted through the bolt insertion hole, which is received within the housing, which is arranged to be rotated relative to the housing, and which separates the operation hydraulic chamber to a retard angle operation chamber and an advance angle operation chamber; a lock hole formed on an inner end surface of the housing; a lock member which is disposed within a sliding movement hole formed in the vane rotor in an axial direction, which is arranged to be moved within the sliding movement hole, and which includes an axial tip end portion that is arranged to be engaged with the lock hole to lock a relative rotation position of the vane rotor with respect to the housing, or to be disengaged from the lock hole to release the lock; an urging member which is disposed within a back pressure chamber provided on a front side of the sliding movement hole that is opposite to the cam shaft, and which is arranged to urge the lock member toward the lock hole; a connection passage provided to the vane rotor, and connected to the bolt insertion hole and the back pressure chamber; and an annular passage which is formed between an inner circumference surface of the bolt insertion hole, and an outer circumference surface of a shaft portion of the cam bolt, and which includes one end portion connected to the connection passage, and the other end portion connected to a drain hole formed in the cam shaft.

Benefit of the Invention

By the present invention, it is possible to suppress the increase of the radial size of the device.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a sectional view showing a valve timing control device according to one embodiment of the present invention.

FIG. 2 is an exploded perspective view showing a part of the valve timing control device according to the embodiment.

FIG. 3 is a front view showing a state where the valve timing control device according to the embodiment is controlled to a retard angle side, and where a front plate is detached.

FIG. 4 is an enlarged view showing a main part of the valve timing control device shown in FIG. 1.

FIG. 5 is a sectional view taken along a section line A-A of FIG. 1.

DESCRIPTION OF EMBODIMENTS

Hereinafter, one embodiment in which a valve timing control device for an internal combustion engine according to the present invention is applied to an intake valve side is explained with reference to the drawings.

As shown in FIG. 1 to FIG. 4, this valve timing control device includes a timing pulley 1 arranged to be driven and rotated through a timing belt by a crank shaft (not shown) of the engine; a cam shaft 2 arranged to be relatively rotated relative to the timing pulley 1; a phase varying mechanism 3 disposed between the timing pulley 1 and the cam shaft 2, and arranged to convert a relative rotational phase between the timing pulley 1 and the cam shaft 2; and a lock mechanism 4 arranged to lock an actuation of the phase varying mechanism 3.

The timing pulley 1 is integrally formed with a housing main body 11 described later. The timing pulley 1 includes a plurality of gear portions 1 a which are integrally formed with the timing pulley 1, and which includes an outer circumference on which the timing belt (not shown) is wound.

The cam shaft 2 is rotatably supported through cam bearings by a cylinder head (not shown). The cam shaft 2 includes a plurality of driving cams which are integrally formed with the cam shaft 2 at predetermined positions of an outer circumference of the cam shaft 2, and which are arranged to open intake valves (not shown) against spring forces of valve springs. Moreover, this cam shaft 2 includes a bolt hole 2 b which is formed in one end portion 2 a in an axial direction, and into which a shaft portion 6 b of a cam bolt 6 (described later) is inserted. This bolt hole 2 b includes an internal screw 2 c which is formed on a tip end side of the bolt hole 2 b, and into which an external screw portion 6 b formed on an outer circumference surface of a tip end portion of the shaft portion 6 b is screwed.

The cam bolt 6 includes a hexagonal head portion 6 a; the shaft portion 6 b integrally formed with one end portion of the head portion 6 a through a flange-shaped seat portion 6 c; and the external screw portion 6 d formed on the outer circumference of the tip end portion of the shaft portion 6 b.

The phase varying mechanism 3 includes the housing 5 disposed on a side of one end portion 2 a of the cam shaft 2; a vane rotor 7 which is fixed to the one end portion 2 a of the cam shaft 2 by the cam bolt 6 from the axial direction, and which is received within the housing 5 to be relatively rotated relative to the housing 5; four retard angle hydraulic chambers 9 and four advance angle hydraulic chambers 10 which are retard angle operation chambers and advance angle operation chambers, which are formed within the housing 5, and which are separated by first to fourth shoes 8 a to 8 d integrally provided on an inner circumference surface of the housing main body 11 described later, and four vanes 22 to 25 (described later) of the vane rotor 7; and a hydraulic circuit arranged to selectively supply and discharge the hydraulic pressure to and from the retard angle hydraulic chambers 9 and the advance angle hydraulic chambers 10.

The housing 5 includes the housing main body 11 which has a substantially cylindrical shape having both axial opening ends; a front plate 12 closing a front end axial opening of the housing main body 11; a rear plate 13 closing a rear end axial opening of the housing main body 11. The housing main body 11, the front plate 12, and the rear plate 13 are integrally jointed by being tightened together by four bolts 14 from the axial direction.

The housing main body 11 is integrally formed from sintered metal. The housing main body 11 includes the outer circumference to which the timing pulley 1 is integrally provided; and the inner circumference surface on which the first to fourth shoes 8 a to 8 d are integrally provided at a substantially regular interval in the circumferential direction to protrude in the radially inward directions.

Each of the shoes 8 a to 8 d has a substantially trapezoid shape when viewed from a side direction. Each of the shoes 8 a to 8 d includes a seal groove which is formed at the each of the shoes 8 a to 8 d along the axial direction, and in which a substantially U-shaped seal member 16 is mounted and fixed. Moreover, each of the shoes 8 a to 8 d includes a bolt insertion hole 17 which is formed in the axial direction on the outer circumference side of the radial direction of the each of the shoes 8 a to 8 d, that is, within the base end portion side which is a connection portion between the inner circumference surface of the housing main body 11 and the each of the shoes 8 a to 8 d to penetrate through the each of the shoes 8 a to 8 d, and through which one of the bolts 14 is inserted.

The housing main body 11 includes a first seal groove 11 a which is formed on the front end surface of the housing main body 11, which has a biplane shape (compound leaf shape), and in which a first seal member 15 is mounted and fixed. The first seal member 15 is arranged to seal a portion between the front end surface of the housing main body 11 and the front plate 12.

The front plate 12 is formed by forging, casting, or pressing into a relatively thin circular plate shape which is made from a metal. The front plate 12 includes a cylindrical portion 12 a which is integrally formed at a center; and a large diameter hole 12 b which is formed inside the cylindrical portion 12 a , and in which the head portion 6 a of the cam bolt 6 can be mounted. Moreover, the front plate 12 includes four bolt insertion holes 12 c which are formed on the outer circumference side of the front plate 12 at a regular interval in the circumferential direction, which penetrate though the front plate 12, and each of which one of the bolts 14 is inserted through.

Moreover, a plug 18 is mounted to the cylindrical portion 12 a of the front plate 12. The plug 18 closes the large diameter hole 12 b. This plug 18 has a bottomed cylindrical shape. The plug 18 includes a cylindrical portion 18 a which has an outer circumference on which an external screw portion 18 b is formed. The external screw portion 18 b is screwed in the internal screw portion formed on the inner circumference surface of the large diameter hole 12 b. Moreover, the plug 18 includes a hexagonal portion 18 d which is integrally provided with the plug 18, which is formed at a center of an outer surface of a cover wall 18 c, and on which a tool such as a wrench (spanner) is engaged. Furthermore, a seal ring 26 is mounted and fixed between an inner surface of an outer circumference portion of the cover wall 18 c, and the cylindrical portion 12 a.

The rear plate 13 is formed by forging, casting, or pressing into a circular plate shape which is made from a metal. The rear plate 13 includes a support hole 13 a which is an insertion hole, which is formed at a center of the rear plate 13, through which the one end portion 2 a of the cam shaft 2 is inserted to be rotatably supported, and which penetrates through the rear plate 13. Moreover, the rear plate 13 includes four internal screw holes 13 b which are formed on the outer circumference side of the rear plate 13 at a regular interval in the circumferential direction, and which one of the external screw portions of the tip end portions of the bolts 14 is screwed into. A cylindrical portion 13 c is integrally formed with this rear plate 13 on an edge of the support hole 13 a. The cylindrical portion 13 c extends in the axial direction to cover the outer circumference surface of the cam shaft 2.

Furthermore, the rear plate 13 includes four advance angle side oil grooves 19 which are second oil passages, which are formed on an inner end surface of the rear plate 13, each of which is connected to one of the advance angle hydraulic chambers 10, and each of which radially extends from a center of the support hole 13 a. The rear plate 13 includes a second seal groove 13 d which has a biplane (compound leaf) shape, which is formed on the outer circumference side of the inner end surface, and in which a second seal member 27 is mounted and fixed. The second seal member 27 seals a portion between the rear end surface of the housing main body 11 and the rear plate 13.

The vane rotor 7 is integrally formed from the sintered metal. The vane rotor 7 includes a bolt insertion hole 7 a formed at a center of the vane rotor 7; a rotor portion 21 which has a cylindrical shape, and which is fixed to the one end portion 2 a of the cam shaft 2 from the axial direction by the cam bolt 6 inserted into the bolt insertion hole 7 a from the axial direction; and the first to fourth vanes 22 to 25 which are formed on the outer circumference surface of the rotor portion 21 at a substantially regular interval, and which protrude in the radial directions.

The rotor portion 21 is arranged to be rotated so that the outer circumference surface of the rotor portion 21 is slid on the seal members 16 mounted and fixed in the upper surfaces of the tip end portions of the shoes 8 a to 8 d. As shown in FIG. 3, the rotor portion 21 includes four retard angle side oil hole 20 which are formed in the radial direction on the both sides of the respective vanes 22 to 25, each of which penetrates through the rotor portion 21 in the radial direction, and each of which is connected to one of the retard angle hydraulic chambers 9. Furthermore, as shown in FIG. 1 and FIG. 3, the rotor portion 21 includes a first mounting groove 21 a which is formed at a center on an end surface of the rotor portion 21 on a side of the cam shaft 2, and in which the tip end of the one end portion 2 a of the cam shaft 2 is mounted. On the other hand, the rotor portion 21 includes a second mounting groove 21 b which is formed at a center on an end surface of the rotor portion 21 on a side of the front plate 12, and in which the seat portion 6 a of the cam bolt 6 is mounted, as shown in FIG. 1 and FIG. 2. Furthermore, a bottom surface of this second mounting groove 21 b is a seat surface 21 c on which the end surface of the seat portion 6 c is seated.

As shown in FIG. 3, the vanes 22 to 25 are disposed, respectively, between the shoes 8 a to 8 d. Furthermore, each of the vanes 22 to 25 includes the seal groove formed on the tip end surface of the each of the vanes 22 to 25 in the axial direction. A substantially U-shaped seal member 28 is mounted and fixed in each of the seal grooves. The seal members 28 are slidably abutted on the inner circumference surface 11 a of the housing main body 11.

The first vane 22 has a maximum width in these vanes 22 to 25. The other second to fourth vanes 23 to 25 have a substantially identical width which is sufficiently smaller than that of the first vane 22. In this way, the other three vanes 23 to 25 have the width smaller than the maximum width of the first vane 22. With this, it is possible to uniform entire weight balance of the vane rotor 7.

In the first vane 22, when the vane rotor 7 is maximally rotated in the counterclockwise direction as shown in FIG. 3, one end surface of the first vane 22 is abutted on a confronting side surface of the first shoe 8 a so as to restrict the relative rotation position of the first vane 22 on the maximum retard angle side. Moreover, when the vane rotor 7 is maximally rotated in the clockwise direction, the other side surface of the first vane 22 is abutted on a confronting side surface of the second shoe 8 b to restrict the relative rotation position of the vane rotor 7 on the maximum advance angle side.

Besides, when the first vane 22 is abutted on the first and second shoes 8 a , 8 b, the other vanes 23 to 25 are not abutted on any shoes 8 a to 8 d confronting the other vanes 23 to 25 in the circumferential direction.

As shown in FIG. 1 to FIG. 4, the lock mechanism 4 includes a sliding movement hole 29 which is formed in the first vane 22, and which penetrates through the first vane 22 in the axial direction; a lock pin 30 which is a lock member, which is slidably received within the sliding movement hole 29, and which is arranged to be projectable and retractable with respect to the rear plate 13 side; a lock hole 31 which is a lock recessed portion, which is formed at a substantially radially center predetermined portion of the rear plate 13, and in which the tip end portion of the lock pin 30 is engaged to lock the vane rotor 7; and an engagement/disengagement mechanism (engagement/release mechanism) arranged to engage and disengaged the tip end portion of the lock pin 30 with and from the lock hole 31 in accordance with the start condition of the engine.

The sliding movement hole 29 has an inner circumference surface having a stepped shape. The sliding movement hole 29 includes a small diameter hole 29 a on the front end side on a side of the rear plate 13, and a large diameter hole 29 b on the rear end side. Moreover, the sliding movement hole 29 includes a first stepped portion 29 c which has an annular shape, and which are formed between the small diameter hole 29 a and the large diameter hole 29 b.

As shown in FIG. 2 and FIG. 5, the lock pin 30 includes a stepped outer circumference surface corresponding to the lock hole 31 and the sliding movement hole 29. The lock pin 30 includes a small diameter portion 30 a including a tip end portion which is arranged to be slidably moved within the small diameter hole 29 a; a large diameter portion 30 b which is formed on the outer circumference of the rear end portion, and which is slidably moved within the large diameter hole 29 b; and a second stepped portion 30 c which is formed between the small diameter portion 30 a and the large diameter portion 30 b. The tip end portion of the small diameter portion 30 a is solid. An outer circumference of the tip end portion of the small diameter portion 30 a is a cylindrical shape.

A guide ring 31 a is fixed in the inner circumference surface of the lock hole 31 by the press fit. The guide ring 31 a has an annular shape. The guide ring 31 a is arranged to slidably guide the tip end portion of the lock pin 30. Moreover, the lock hole 31 is formed on a side of the advance angle hydraulic chamber 10 in the circumferential direction, that is, at a position at which the lock hole 31 confronts the lock pin 30 in the axial direction when the vane rotor 7 is relatively rotated on the maximum retard angle side. Accordingly, when the lock pin 30 is engaged with the lock hole 31, the relative rotation angle between the housing 5 and the vane rotor 7 becomes a conversion angle of the maximum retard angle which is appropriate for the start of the engine.

Moreover, an annular pressure receiving chamber 33 is formed between the first stepped portion 29 c of the sliding movement hole 29 and the second stepped portion 30 d of the lock pin 30. This pressure receiving chamber 33 constitutes a part of a disengagement (release) oil passage described later.

Furthermore, the sliding movement hole 29 includes a back pressure chamber 29 d which is formed in a rear end portion of the sliding movement hole 29, and which is separated in cooperation with the lock pin 30.

The engagement/disengagement mechanism includes a coil spring 32 which is elastically mounted between an inner bottom surface of a cylindrical groove formed on a rear end side of the lock pin 30 in the axial direction, and an inner end surface of the front plate 12, and which is arranged to urge the lock pin 30 in the projecting direction (toward the lock hole 31); and a disengagement passage which is arranged to supply the hydraulic pressure into the pressure receiving chamber 33, and thereby to retract the lock pin 30 against a spring force of the coil spring 32.

When the vane rotor 7 is relatively rotated to the maximum retard angle phase position, the coil spring 32 moves the lock pin 30 by the spring force in the projecting (forward) direction so that the tip end portion of the lock pin 30 is inserted and engaged with the lock hole 31. With this, the vane rotor 7 is locked with respect to the housing 5.

As shown in FIG. 3, the disengagement passage includes a first oil hole 41 a and a second oil hole 41 b which are formed in the first vane 22 in the circumferential direction to sandwich the sliding movement hole 29, and which are arranged to supply the hydraulic pressures supplied to the retard angle hydraulic chamber 9 and the advance angle hydraulic chamber 10 to the pressure receiving chamber 33.

That is, the first oil hole 41 a is formed in the first vane 22 in the widthwise direction to extend from one end opening formed in the one end surface of the first vane 22 which confronts one of the advance angle hydraulic chambers 10, to the other end opening confronting the pressure receiving chamber 33. On the other hand, the second oil hole 41 b is similarly formed in the first vane 22 in the widthwise direction to extend from the one end opening formed on the other end surface of the first vane 22 which confronts the retard angle hydraulic chamber 9, to the other end opening confronting the pressure receiving chamber 33 in an opposite direction.

The hydraulic pressure supplied from the oil holes 41 a and 41 b to the pressure receiving chamber 33 is acted on the second stepped portion 30 c to move the lock pin 30 against the spring force of the coil spring 32 in the engagement release direction, that is, in the retracting direction (rearward direction). With this, the engagement of the tip end portion of the lock pin tip end portion with respect to the lock hole 31 is released to allow the free relative rotation of the vane rotor 7 with respect to the housing 5.

Moreover, a positioning means is provided between the cam shaft 2 and the vane rotor 7. The positioning means is arranged to position the cam shaft 2 and the vane rotor 7 in the circumferential direction when the cam shaft 2 and the vane rotor 7 are tightened by the cam bolt 6.

As shown in FIG. 1 and FIG. 4, this positioning means includes a positioning pin 50 which has a base end portion fixed, by the press fit, in a pin fixing hole 35 a (a part of an advance angle side passage 35 described later) formed in the cam shaft 2 from the tip end surface 2 a in the axial direction; and a positioning hole 51 which has a U shape, which is formed in the rotor portion 21 to penetrate from the seat surface 21 c of the second mounting groove 21 to the first mounting groove 21 a , and in which the tip end portion 50 a of the positioning pin 50 is engaged.

The hydraulic circuit is arranged to selectively supply the hydraulic pressure to the advance angle hydraulic chambers 9 and the retard angle hydraulic chambers 10, or to selectively discharge the hydraulic pressure from the advance angle hydraulic chambers 9 and the retard angle hydraulic chambers 10. Specifically, as shown in FIG. 1 and FIG. 5, the hydraulic circuit includes a pair of retard angle side passages 34 each of which is formed in the cam shaft 2 from the one end portion 2 a in the axial direction and in the radial direction, and which are connected to the retard angle side oil holes 20; a pair of advance angle side passages 35 which are formed in the cam shaft 2 from the one end portion 2 a in the axial direction and in the radial direction in parallel with the retard angle passages 34, and which are connected to the advance angle side oil grooves 19; an electromagnetic switching valve 36 provided between the passages 34 and 35; an oil pump 37 arranged to selectively supply the hydraulic pressure through the electromagnetic switching valve 36 to the passages 34 and 35; and a drain passage 38 selectively connected through the electromagnetic switching valve 36 to the retard angle side passages 34 and the advance angle side passages 35. Besides, a suction passage 37 a of the oil pump 37 and the drain passage 38 are connected to an oil pan 39.

The retard angle side passage 34 includes one end portion connected to a retard angle port of the electromagnetic switching valve 36; and the other end portion connected through a groove (not shown) to the oil grooves 20. The advance angle side passage 35 includes one end portion connected to an advance angle port of the electromagnetic switching valve 36; and the other end portion connected through a groove (not shown) to the oil grooves 19.

The electromagnetic switching valve 36 is four-port three-position valve. The electromagnetic switching valve 36 is arranged to selectively control and switch among the retard angle port, the advance angle port, the discharge passage 37 a of the oil pump 37, and the drain passage 38, by an output signal from a controller (not shown).

The controller includes an inside computer configured to receive information signal from various sensors such as a crank angle sensor (not shown), an air flow meter (not shown), a water temperature sensor (not shown), a throttle valve opening degree sensor (not shown), to sense a current engine driving state, and to output a control current to a solenoid of the electromagnetic switching valve 36 in accordance with this engine driving state.

Besides, in FIG. 1, a numeral 40 is a pressure regulating valve of a pilot type which is provided on a downstream side of the discharge passage 37 b of the oil pump 37. A numeral 41 is a filter.

Moreover, a discharge means is provided to the rotor portion 21 and the first vane 22 of the vane rotor 7, the cam shaft 2, and so on. The discharge means is arranged to connect the back pressure chamber 29 d of the sliding movement hole 29 and the outside, and thereby to discharge the hydraulic fluid and the air flowing into the back pressure chamber 29 d to the outside to ensure the good slidability of the lock pin 30 within the sliding movement hole 29.

As shown in FIG. 1 to FIG. 4, this discharge means includes a radial groove 52 which is a second connection groove, and which is formed in the radial direction on a front end surface of the first vane 22 on the side of the front plate 12 from an inner end edge of the back pressure chamber 29 d; an axial groove 53 which is a first connection groove, which is formed in the axial direction on the rotor portion 21 along the inner circumference surface of the second mounting groove 21 b, and which includes one end connected to the radial groove 52; a passage groove 54 which is formed between the axial groove 53 and the positioning groove 51, and which is formed in the radial direction on the seat surface 21 c on which the seat portion 6 c of the cam bolt 6 is seated; an annular passage 55 which is an annular passage, which is formed between the inner circumference surface of the bolt insertion hole 7 a of the rotor portion 21, and the shaft portion 6 b, and which is connected through the positioning hole 51 to the passage groove 54; a discharge passage 56 which has a cylindrical shape, which is formed between the inner circumference surface of the bolt hole 2 b of the cam shaft 2, and the outer circumference surface of the cam bolt 6, and which includes an axial one end portion 56 a connected to the annular passage 55; a drain hole 57 which is formed in the one end portion 2 a of the cam shaft 2 in the radial direction to penetrate through the one end portion 2 a of the cam shaft 2, and which includes an inner end opening connected to the other end side of the discharge passage 56.

Moreover, the rear plate 13 includes a drain groove 58 which has a cylindrical shape, and which is formed in the axial direction on the inner circumference surface of the cylindrical portion 13 c of the rear plate 13. This drain groove 58 includes an axial one end portion 58 a which is opened and formed near a flange portion 2 d integrally provided on an outer circumference of the one end portion 2 a of the cam shaft 2, and which is connected to the outside.

The radial groove 52 is connected to the axial groove 53 in the perpendicular direction. The radial groove 52 includes one end opening confronting a side end edge of the back pressure chamber 29 d.

The axial groove 53 is formed in the axial direction to the seat surface 21 c merely by cutting a part of the inner circumference surface of the second mounting groove 21 b of the rotor portion 21. The axial groove 53 has a short axial length. The axial groove 53 includes an inner end side confronting the end edge of the positioning hole 51.

The radial groove 52, the axial groove 53, the passage groove 54, and the positioning hole 51 are formed into a crank shape. The radial groove 52, the axial groove 53, the passage groove 54, and the positioning hole 51 are continuously connected to the discharge passage 56, the drain hole 57, and the drain groove 58 on the downstream side.

[Operations in This Embodiment]

Hereinafter, operations of this embodiment are explained. Firstly, a pump operation of the oil pump 37 is stopped at the stop of the engine, so that the supply of the hydraulic fluid to the hydraulic chambers 9 and 10 are stopped. Accordingly, as shown in FIG. 3, the vane rotor 7 is relatively rotated to the maximum retard angle position by alternating torque acted to the cam shaft 2. At this position, the tip end portion of the lock pin 30 is inserted and engaged in the lock hole 31 by the spring force of the coil spring 32, so as to lock the vane rotor 7 to the maximum retard angle side position appropriate for the start.

Next, when the ignition switching is switched to the ON state to initiate the start, that is, in an initial stage of the cranking, the controller maintains deenergization state of the coil of the electromagnetic switching valve 36. With this, as shown in FIG. 1, the discharge passage 37 b of the oil pump 37, and the retard angle side passage 34 are connected with each other. Simultaneously, the advance angle side passage 35 and the drain passage 38 are connected with each other.

Accordingly, the hydraulic fluid discharged from the oil pump 37 flows through the electromagnetic switching valve 36 and the retard angle side passage 34 to the retard angle hydraulic chambers 9, so that the retard angle hydraulic chambers 9 become high pressure. On the other hand, the hydraulic fluid within the advance angle hydraulic chambers 10 flows through the advance angle side passage 35 and the drain passage 38 to the oil pan 39, so that the advance angle hydraulic chambers 10 become the low pressure.

Consequently, the lock state of the vane rotor 7 is maintained in the initial stage of the cranking of the start of the engine. The vane rotor 7 becomes the maximum retarded angle relative rotation position. Therefore, it is possible to obtain good startability by the smooth cranking, to suppress the flapping (fluttering), and to suppress the interference between the vanes 22 to 25 and the shoes 8 a to 8 d. Accordingly, it is possible to sufficiently suppress the tap noise (hammering noise) due to the interference. In particular, it is possible to sufficiently suppress the tap noise (hammering noise) between the first vane 22 and the shoes 8 a and 8 b.

The pump discharge pressure is supplied from the oil holes 20 to the retard angle hydraulic chambers 9. Moreover, this hydraulic pressure flows from the second connection hole 41 b to the pressure receiving chamber 33, so that the pressure receiving chamber 33 becomes the high pressure. With this, the lock pin 30 is moved in the retracting direction (rearward direction) so that the tip end portion of the lock pin 30 is pulled out of the lock hole 31. Consequently, it is possible to ensure the free relative rotation of the vane rotor 7 with respect to the housing 5.

However, when the vane rotor 7 is rotated in the counterclockwise direction as shown in FIG. 3 in accordance with the expansion of the volumes of the retard angle hydraulic chambers 9, the one side surface of the first vane 22 is abutted on the confronting side surface of the first shoe 8 a so as to restrict the further rotation of the vane rotor 7 in the counterclockwise direction. With this, the relative rotation angle of the vane rotor 7, that is, the cam shaft 2 with respect to the housing 5 (the timing pulley 1) is maintained to the maximum retard angle side.

Next, when the engine is shifted to the predetermined engine driving state such as the idling state, the controller outputs the control current to the electromagnetic switching valve 36 to start the actuation of the electromagnetic switching valve 36. With this, the discharge passage 37 b and the advance angle side passage 35 are connected with each other. Simultaneously, the retard angle side passage 34 and the drain passage 38 are connected with each other. With these, the hydraulic fluid within the retard angle hydraulic chambers 9 are discharged so that the retard angle hydraulic chambers 9 become the low pressure. Moreover, the hydraulic pressure is supplied to the advance angle hydraulic chambers 10, so that the advance angle hydraulic chambers 10 become the high pressure. At this time, the hydraulic pressure is supplied from one of the advance angle hydraulic chambers 10 through the first connection hole 41 a to the pressure receiving chamber 33. Accordingly, the lock pin 30 is maintained to be pulled out of the lock hole 31 by this hydraulic pressure.

Therefore, the vane rotor 7 is relatively rotated relative to the housing 5 in the clockwise direction, so that the other end surface of the first vane 22 is abutted on the confronting side surface of the second shoe 8 b so as to restrict the further rotation of the vane rotor 7 in the clockwise direction. With this, the relative pivot phase of the cam shaft 2 with respect to the timing pulley 1 is converted to the maximum advance angle side. Consequently, the opening and closing timings of the intake valves are controlled to the maximum advance angle side. It is possible to improve the performance of the engine in this driving region.

Furthermore, in this embodiment, the oil and the air which flow into the back pressure chambers 29 d flows from the radial groove 52 through the axial groove 53, the passage groove 54, the positioning hole 51, and the annular passage 55 to the discharge passage 56. Moreover, it is possible to rapidly discharge the oil and the air to the outside through the drain hole 57, the drain groove 58, the flange portion 2 d formed on the outer circumference of the one end portion 2 a of the cam shaft 2, and so on, and thereby to improve the axial movement of the lock pin 30, that is, the engagement/disengagement movement with respect to the lock hole 31.

Moreover, the passage and so on which are the discharge means is not formed in the rotor portion so as to penetrate through the rotor portion in the axial direction, like the connection hole in the above-described conventional art. The discharge means is the axial groove 53 which has the short length, and which is formed on the inner circumference surface of the second mounting groove 21 b formed in the rotor portion 21, and the existing positioning hole 51. Furthermore, the discharge passage 56 is formed by using a gap between the inner circumference surface of the bolt hole 2 b of the cam shaft 2, and the outer circumference surface of the shaft portion 6 b of the cam bolt 6. Accordingly, it is sufficiently decrease the radial size of the rotor portion 21.

That is, in a case where a part of the discharge means is formed in the rotor portion 21 to penetrate through the rotor portion 21 in the axial direction, it is necessary to increase the outside diameter of the rotor portion 21 so as to ensure the forming space of the discharge means. However, in this embodiment, the axial groove 53 which is a part of the discharge means is formed by using the inner circumference surface of the second mounting groove 21 b without penetrating through the rotor portion 21. Moreover, a part of the existing positioning hole 51 is used as the passage. Moreover, the discharge passage 56 is formed by using the cylindrical gap between the inner circumference surface of the cam shaft 2 and the outer circumference surface of the cam bolt 6. Accordingly, it is utterly unnecessary to increase the outside diameter of the rotor portion 21. Consequently, it is possible to suppress the size increase of the entire device.

Moreover, the inner circumference surface of the existing second mounting groove 21 b, the existing positioning hole 51, the existing cam shaft 2, and the existing cam bolt 6 are used. Accordingly, it is unnecessary to form a special passage. Consequently, it is possible to ease the manufacturing operation, and to suppress the increase of the cost. In particular, the radial groove 52, the axial groove 53, the passage groove 54, the second mounting groove 21 b, and the positioning groove 51 are formed together within the die at the sinter-forming of the vane rotor 7. Consequently, it is possible to ease these processing operations.

Moreover, the drain hole 57 is formed by the drill tool to penetrate in the radial direction to pass through the center of the cam shaft. Accordingly, this processing operation is easy.

The passage groove 54 between the axial groove 53 and the positioning hole 51 is formed by cutting the seat surface 21 c on which the seat portion 6 of the cam bolt 6 is seated, from the radial direction. Accordingly, it is possible to sufficiently ensure the effective area of the seat surface 21 c, and thereby to suppress the decrease of the tightening force of the cam bolt 6.

Each of the advance angle side oil grooves 19 is formed in the inner end surface of the rear plate 13 in the radial direction. Accordingly, it is unnecessary to increase the axial length. Consequently, it is possible to decrease the axial length of the device.

Moreover, the oil discharged from the drain hole 57 to the outside is received by the bottom surface of the drain groove 58. Then, the oil is guided toward the flange portion 2 d of the cam shaft 2. Furthermore, the oil flows on the outer surface of the flange portion 2 d, and discharges to the outside. That is, the oil discharged from the drain hole 57 is guided by the drain groove 58 to be sufficiently apart from the timing pulley 1 in the axial direction of the cam shaft 2. Then, the oil is adhered on the outer surface of the flange portion 2 d. The oil adhered on the outer surface of this flange portion 2 d is dispersed from the outer circumference edge of the flange portion 2 to the outside by the centrifugal force at the rotation of the cam shaft 2. Consequently, the discharged oil is not adhered to the timing pulley 1. Therefore, it is possible to suppress the generation of the slip and so on between the gear portions 1 a of the timing pulley 1, and the timing belt.

In this embodiment, the hydraulic pressure from the retard angle hydraulic chambers 9 and the hydraulic pressure from the advance angle hydraulic chambers 10 are used for releasing the lock of the lock pin 30. However, it is optional to use only the hydraulic pressure from the retard angle hydraulic chambers 9. Moreover, in a case where this valve timing control device is provided on the exhaust valve side, the discharge hydraulic pressure of the oil pump is supplied to the advance angle hydraulic chambers 10 at the initial stage of the start of the engine. Accordingly, it is optional to use only the hydraulic pressure from one of the advance angle hydraulic chambers 10. 

1. A valve timing control device for an internal combustion engine, the valve timing control device comprising: a housing to which a rotational force is transmitted from a crank shaft, and which includes an operation hydraulic chamber formed therein; a vane rotor which includes a bolt insertion hole, which is fixed at one end portion of a cam shaft by a cam bolt inserted through the bolt insertion hole, which is received within the housing, which is arranged to be rotated relative to the housing, and which separates the operation hydraulic chamber to a retard angle operation chamber and an advance angle operation chamber; a lock hole formed on an inner end surface of the housing; a lock member which is disposed within a sliding movement hole formed in the vane rotor in an axial direction, which is arranged to be moved within the sliding movement hole, and which includes an axial tip end portion that is arranged to be engaged with the lock hole to lock a relative rotation position of the vane rotor with respect to the housing, or to be disengaged from the lock hole to release the lock; an urging member which is disposed within a back pressure chamber provided on a front side of the sliding movement hole that is opposite to the cam shaft, and which is arranged to urge the lock member toward the lock hole; a connection passage provided to the vane rotor, and connected to the bolt insertion hole and the back pressure chamber; and an annular passage which is formed between an inner circumference surface of the bolt insertion hole, and an outer circumference surface of a shaft portion of the cam bolt, and which includes one end portion connected to the connection passage, and the other end portion connected to a drain hole formed in the cam shaft.
 2. The valve timing control device for the internal combustion engine as claimed in claim 1, wherein the connection passage includes a first connection groove that is formed in a radial direction on a seat surface which is a front end surface of the vane rotor, on which a head portion of the cam bolt is seated, and that includes one end connected to the back pressure chamber, and the other end connected to the annular passage.
 3. The valve timing control device for the internal combustion engine as claimed in claim 2, wherein the connection passage includes a second connection groove which is formed in the radial direction on the front end surface of the vane rotor in the radial direction, and which includes one end connected to the back pressure chamber, and the other end connected to the first connection groove.
 4. The valve timing control device for the internal combustion engine as claimed in claim 3, wherein the first connection groove is formed to penetrate in the axial direction; a positioning pin fixed to the one end portion of the cam shaft extends to the first connection groove.
 5. The valve timing control device for the internal combustion engine as claimed in claim 3, wherein the first connection groove and the second connection groove are formed to be bent into a crank shape in a longitudinal section; and the first connection groove and the second connection groove are formed between an inner surface of a front plate closing a front end opening of a housing main body of the housing, and an inner surface of a flange-shaped seat portion of a head portion of the cam bolt.
 6. The valve timing control device for the internal combustion engine as claimed in claim 1, wherein the cam shaft includes a bolt hole which is formed in the cam shaft in the axial direction, and through which the shaft portion of the cam bolt is inserted, and a discharge passage which is formed between an inner circumference surface of the bolt hole, and an outer circumference surface of the shaft portion of the cam bolt, and which includes one end portion connected to the annular passage, and the other end portion connected to the drain hole; and the discharge passage is constituted by a cylindrical gap formed between the inner circumference surface of the bolt hole and the outer circumference surface of the shaft portion of the cam bolt.
 7. The valve timing control device for the internal combustion engine as claimed in claim 6, wherein the bolt hole is formed at a position to confront the bolt insertion hole of the vane rotor in the axial direction.
 8. The valve timing control device for the internal combustion engine as claimed in claim 7, wherein the housing includes a cylindrical portion that is formed on an opening edge of an insertion hole into which the cam shaft is inserted, and that extends in the axial direction along the outer circumference surface of the cam shaft, and a groove portion formed on an inner circumference surface of the cylindrical portion; the drain hole is formed from a side of the discharge passage in a radially outward direction of the cam shaft; and the drain hole includes an outer end opening confronting the groove portion.
 9. The valve timing control device for the internal combustion engine as claimed in claim 1, wherein the cam shaft includes a retard angle passage and an advance angle passage which are formed in the cam shaft; the vane rotor includes a first oil passage arranged to connect one of the retard angle passage and the advance angle passage, and one of the retard angle operation chamber and the advance angle operation chamber; and the housing includes a second oil passage arranged to connect the other of the retard angle passage and the advance angle passage, and the other of the retard angle operation chamber and the advance angle operation chamber. 